Zika virus vaccine for animals brings hope for human protection

Trial version in US giving successful immunisation to mice could help fight disease, but complications warned for those who have contracted dengue fever

An experimental vaccine that completely protects animals from the Zika virus has raised hopes for a jab that can bring the fast-spreading disease under control.
Trials in the US found that a single immunisation shot made from a purified and inactivated form of the Zika virus gave mice total protection against the illness that has swept through Brazil and other parts of South America.
The race is now on to convert this early success into an effective human vaccine, but that may not be straightforward. The similarity of the Zika virus to others in circulation means the vaccine may prove less effective in some people, and could potentially make other infections, such as dengue fever, more serious. Those concerns will almost certainly have to be addressed before human trials can begin.

Dan Barouch, who led the study at Beth Israel Deaconess Medical Center in Boston, called the trial results “a step forwards in the development of a Zika virus vaccine”, but said more research lay ahead. “Of course we need to be cautious about extrapolating results from mice into humans,” he said.
The vaccine is one of a number that have been under development as a top priority since the World Health Organisation in February declared the Zika epidemic a global public health emergency. Mosquitoes in more than 60 countries now carry the virus linked to severe birth defects and a paralysing neurological disorder called Guillain-Barré syndrome.
Writing in the journal, Nature, Barouch and colleagues describe how they tested two experimental Zika vaccines in mice. The first, known as a DNA vaccine, was made from genetic material taken from Zika virus circulating in the Brazil outbreak. The second was a more conventional vaccine, made from whole inactivated Zika virus in Puerto Rico. Both vaccines protected mice for at least two months.
“We were very surprised and quite impressed that a single shot of either one of these vaccines provided complete protection,” said Barouch. Tests are now underway to understand how long the vaccines are effective for, and whether boosters can extend the protection they offer.